This invention is directed to sunscreen formulations comprising copolymers of isoprene, butadiene and or styrene which have improved water resistance. More particularly, this invention is directed to sunscreen formulations comprising liquid block copolymers having unsaturation only on the terminal blocks and methods of preparation thereof for use in sunscreen.
U.S. Pat. No. 5,204,090 describes waterproof sunscreens comprising a water insoluble film forming polymer. U.S. Pat. No. 5,653,965 describes film forming polymers for sunscreen spray. U.S. Pat. No. 5,487,886 describes acryl polymers for sunscreen formulations. U.S. Pat. No. 5,145,669 describes water proof sunscreens containing a crosslinked, neutralized terpolymer of maleic anhydride, a C1-C5 alkyl vinyl ether and a C12-C14 alpha-olefin monomer. U.S. Pat. No. 4,663,157 describes a copolymer of ethylene and acrylic acid for use in sunscreen compositions.
Sunscreen products are usually applied prior to activities such as bathing or sports. The product will remain effective after exposure to water and/or perspiration. The use of water insoluble active sunscreen ingredients is usually insufficient to provide adequate water resistance. A thickener also is required in such formulations. However, an effective method of accomplishing water resistance or water proofing of a sunscreen formula is to employ a water-insoluble substantive film forming resin. A Carbomer resin can provide thickening action. Typical materials for waterproofing sunscreen formulations are two resins which are copolymers of vinylpyrrolidone and long chain alkanes, C16 and C20. They are oil-soluble film forming polymers which have been used for some time by the cosmetic industry.
Therefore, it is the object of the present invention to provide new polymers for sunscreen formulations with improved properties.